1. Field of the Invention
The present invention relates generally to a semiconductor structure and process for forming a plug, and more specifically to a semiconductor structure and process applying a layers-pulling back process for forming a plug.
2. Description of the Prior Art
Field effect transistors are important electronic devices in the fabrication of integrated circuits, and as the size of the semiconductor device becomes smaller and smaller, the fabrication of the transistors also improves and is constantly enhanced for fabricating transistors with smaller sizes and higher quality. In the conventional method of fabricating transistors, a gate structure is first formed on a substrate, and a lightly doped drain (LDD) is formed on the two corresponding sides of the gate structure. Next, a spacer is formed on the sidewall of the gate structure and an ion implantation process is performed to forma source/drain region within the substrate by utilizing the gate structure and spacer as a mask. In order to incorporate the gate, source, and drain into the circuit, contact plugs are often utilized for interconnection purposes. Each of the contact plugs include a barrier layer surrounding a low resistivity material to prevent the low resistivity material from diffusing outward to other areas. As the miniaturization of semiconductor devices increases, filling the barrier layer and the low resistivity into a contact hole has become an important issue to form the contact plug and maintaining or enhancing the performances of formed semiconductor devices as well.